The use of individual vital sign monitoring by individual instruments to assess patient condition has existed for many decades.
Many vital sign variables such as heart rate, blood pressure, pulse pressure and pulse volume are routinely monitored in modern medicine, especially before, during or after an operation. These variables may be displayed numerically or graphed to allow a medical professional to assess the absolute as well as rate or magnitude of change over time of these variables.
Present anaesthetic monitors often include threshold alarms with fixed default values and/or user adjustable values to alert an anaesthetist when the threshold value has been exceeded. Unfortunately, though the fact a threshold has been exceeded is important, it is not necessarily indicative of a problem unless supported by a change in other vital signs, trends or visual observations, and as such many alerts are simply false alarms. The frequency of false alerts means these threshold alarms can be either turned off or ignored, the anaesthetist relying on careful monitoring to react to important changes. The interpretation of the monitor output, and changes over time, depend on the skill and experience of the anaesthetist.
An additional problem with threshold alarms is that the relevant threshold value may change during an operation as other variables change. In addition the relevant threshold often depends on the patient concerned and as such for certain patients a default threshold may be inappropriate. This means that the setting of the threshold value, if not locked to a default, depends on the skill and experience of the anaesthetist.
A further problem with many sensors or monitoring devices is the difference in data collection rates each provide. Some sensors and/or monitoring devices provide a nearly continuous data stream, others provide an output many times a second and still others every second, every minute or longer. This variation in data output rates can make it difficult to combine data from a multitude of monitoring devices, certainly it can require a great deal of skill. In fact for some monitoring devices the data collection frequency may not be apparent or disclosed.
Any discussion of the prior art throughout the specification is not an admission that such prior art is widely known or forms part of the common general knowledge in the field.